How to Calculate Density to Spot Fake Gold 🎬

When the shape of the object whose volume we want to measure is irregular or has reliefs that make this difficult, we need to find an alternative method.

We might think of immersing our object in a container and calculating its volume by measuring the difference in the water level. However, this method is very imprecise and uncomfortable for objects. However, there is a way that makes this measurement easier: using Archimedes’ principle.

👉 Read also: Test to Check Investment Gold and Silver 🎬

---

#1. Theory

Archimedes left us a precious formula as a legacy:

A body immersed in a fluid receives an upward thrust equal to the weight of the volume of fluid displaced.

For those of you who love to bathe in the tub and occasionally like to play with empty shampoo bottles, you will have noticed that when you try to immerse the empty plastic bottle (but full of air) there is a resistance that opposes our hand. This resistance is the weight of the displaced water.

If we could therefore measure this force, knowing the density of water, we could obtain the volume of the object we want to verify. Reversing the formula to calculate density, we obtain:

Density = Mass / Volume → Volume = Mass / Density

Since the density of water is equal to 1 g/cm³, it will be sufficient to read the value measured on the scale screen to obtain the volume of the immersed object in cm3.

---

#2. Pratice

Now that we have learned the basics, let’s get down to business. We will need:

• a high-precision or high-capacity scale, whose capacity and precision vary depending on the size of the object we need to measure. I assume that mass is measured in grams (g).
• a plastic basin, whose size varies depending on the size of the object we need to measure.
• a very thin string such as sewing thread, which takes up as little space as possible but is strong enough to support the mass of our suspended object.

---

Procedure

Let’s place the basin on our scale and fill it with water (possibly distilled at 20 °C for a more precise measurement) so that it can cover the size of our immersed object but without exceeding.

Let’s tare the scale, tie our object to the string and lower it from above, completely immersing it without letting it touch the bottom.

Now let’s read the value shown by the scale and write it down. Let’s remove the basin and instead measure this time the mass of the object that we have just immersed.

Now we have two values:

• the first that we measured is the volume of the object in grams (cm3)
• the second that we measured is the mass of the object in cubic centimeters (g)

At this point we will simply divide the mass by the volume to obtain the density of the object. Now we can compare the density obtained with that of the main metals and understand if the object that we measured can actually correspond to what we expected it to be.

---

Comparison of data

I have created a table showing the density values ​​of all precious metals and those used to make fake coins and ingots:

👉 Read also: Parameters for Precious Metal Verification 📊

However, pay close attention to tungsten which has a density very similar to that of gold:

• Gold: 19.32 g/cm3
• Tungsten: 19.25 g/cm3

In order to detect the presence of tungsten, we will need to check our object with other tests such as: diamagnetism, sound frequency and speed of itsno.

---

#3. The hydrostatic balance

A tool specifically designed for this type of use is known as a hydrostatic balance. This is a highly specialized device, mainly used in professional settings, which guarantees considerable precision during measurements. However, this tool has some aspects to consider: not only does it involve rather high costs, but it also takes up significant space, making it less practical for home or occasional use.

Hydrostatic balances are commonly used in metal banks and gold buyers, where it is essential to carry out accurate assessments of the purity and specific weight of precious metals. Thanks to their reliability, these tools allow you to obtain extremely precise data, essential in commercial and professional contexts.

However, it is important to underline that, although they are very effective tools, they are not always essential for those who want to perform simple checks in an amateur context. The procedure I illustrated previously, although simpler and more accessible, still represents an adequate solution to achieve our goals. Although it does not guarantee the same precision as a hydrostatic balance, it still allows you to obtain satisfactory results, especially when extreme accuracy in measurements is not required.